1. Field of the Invention
The present invention relates to a rotary blade capable of a damping of noises generated during rotation, and further relates to a construction of the rotary blade useful for cutting a stone, concrete, asphalt and the like.
2. Prior Art
A rotary blade capable of damping noises has been disclosed in Japanese Patent Publication No. Sho 50-10040. In this rotary blade, a plurality of grooves having a suitable width, for example 1.5 m, and a suitable length, for example about 10% of an outside diameter of a saw member, are formed at regular intervals from the vicinity of a base portion toward almost a center of the blade on a circumferential edge of the rotary substrate. The respective grooves are filled with setting synthetic resins having a hardness lower than that of the rotary substrate to fixedly mount the setting synthetic resins on the grooves.
It has been described that, according to this construction, low sound waves generated from the setting synthetic resin layer interfere with sound waves generated from the blade to hinder the tuning and resonance of sound waves, thereby changing simple high sounds to complicated low sounds, and thus high and sharp metal sounds are deadened, as a whole.
The blade formed on the circumferential portion of the rotary substrate is rotated at a high speed to produce a turbulent air flow, thereby generating sounds. The blade thus receives an external force resulting from the generation of this turbulent flow to be vibrated, or receives an external force resulting from a load on a material to be cut to be compulsorily vibrated, and thus this vibration is resonant with vibration of the rotary substrate to generate large sounds. According to the Japanese Patent Publication No. Sho 50-10040, a plurality of grooves are formed from the vicinity of the base portion toward almost the center of the blade portion and filled with setting synthetic resins having a hardness lower than that of the blade to act as a buffer zone for the propagation of vibration, thereby partially stopping the propagation of vibration in the rotary substrate, and thus reducing also the resonance.
However, according to the Japaneses Patent Publication No. Sho 50-10040, the buffer zone of vibration is arranged in a radial direction from the center, so that the vibration resulting from the blade portion is damped in the circumferential direction on the rotary substrate, but the vibration generated in the blade portion is reflected in the central portion, whereby the generated vibration can not be sufficiently damped.